1. Field of the Invention
The invention relates to a method for determining an individualized-connection currently allowed transmission rate of ATM cells of virtual connections having variable transmission rates, which utilize time change information allocated to transmission rate changes within an ATM communication system.
2. Description of the Prior Art
A large variety of monitoring procedures are used to monitor variable transmission rates of ATM (asynchronous transfer mode) cells of virtual connections within an ATM communication network (as well as other existing and future packet-oriented communications systems). One such procedure is known as the xe2x80x9cDynamic Generator Cell Rate Algorithm (DGCRA)xe2x80x9d, described in the ITU I.371.1; it is used particularly for ABR (Available Bit Rate) connections within an ATM communication network.
Overload situations in an ATM communication system can be recognized with the assistance of the DGCRA monitoring procedure and measures can be subsequently initiated for eliminating such overload conditions. In order to be able to assure an efficient monitoring of the variable transmission rates for ABR traffic within an ATM communication system, the currently allowed transmission rate (at any specific point in timexe2x80x94generally referred to as xe2x80x9cAllowed Cell Ratexe2x80x9d (ACR)) is continuously required for implementing the DGCRA monitoring procedure. The currently allowed transmission rate of ATM cells thus describes the transmission rate to be monitored at the time of the monitoring procedure.
Connection-related data as well as data describing the current condition of the connection segments are additionally communicated to the receiver via the resource managements cells transmitted in a second communication direction. These are communicated with the assistance of resource management cells (RM), i.e., control cells periodically inserted into the cell stream by a transmission device in a first communication direction opposite the second.
After the arrival of a resource management cell communicated in a second transmission direction in an ATM communication system, a check is carried out (among other things) to see whether the explicit transmission rate entered in the resource management cell can be made available by an ATM communication system for the existing, virtual connection. A further check is carried out to see whether an adaptation of the explicit transmission rate is required in order to avoid a data jam in the ATM communication system. When this is the case, the explicit transmission rate read from the resource management cell is then replaced by the transmission rate that can be communicated from the ATM communication system. This assures that the receiver is informed of the explicit transmission rate by the resource management cell, namely the transmission rate with which data can be sent without causing a traffic jam.
For determining the currently allowed transmission rate, proposal I.371.1, (Traffic Control and Congestion Control in B-ISDN: Conformance Definitions for ABT and ABRxe2x80x9d of the International Telecommunication Union (ITU)) defines, among other things, two individualized-connection delay times providing assistance for calculating the point in time of an increase or, respectively, lowering of transmission rate with respect to the currently allowed transmission rate of ATM cells of a virtual connection. The proposal also explains a method for determining the currently allowed transmission rate of ATM cells with the assistance of three intermediately stored transmission rates and the appertaining time change information.
Applying this method, both the currently allowed transmission rate as well as the appertaining time change information for monitoring this transmission rate are calculated proceeding from the explicit transmission rate of ATM cells read from an incoming resource management cell. The currently allowed transmission rate is adapted to the modified transmission rate with the assistance of counters, two counters are required for each connection for determining a first and a second time change information.
When the counter representing a first time change information runs down, the currently allowed transmission rate is set to the previously determined new value with the assistance of an adaptation routine, and the first time change information is replaced by a second time change information. Subsequently, the updated currently allowed transmission rate of ATM cells is monitored by the DGCRA monitoring procedure until the counter representing a current time change information has run down and a correction of the currently allowed transmission rate is required.
Each virtual connection is provided at least two counters for the realization of the time change information, and at least three memory units for storing the transmission rates for the determination of the respective, per-call, currently allowed transmission rate of ATM cells.
The object of the invention is to improve the determination of the currently allowed transmission rate of ATM cells of virtual connections of an ATM communication system. This object is achieved by utilizing time change information allocated to transmission rate changes within an ATM communication system for determining the individualized-connection currently allowed transmission rate, intermediately storing a determined individualized-connection transmission rate of ATM cells, if it exists, in a memory unit, intermediately storing time change information relating to the transmission rate, if the time change information exists, in the memory unit, calculating the time change information using two individualized-connection prescribable delay times and utilizing a transmission rate handling routine, updating the time change information if it upwardly exceeds a predetermined time span by an updating routine, utilizing a current time value of a calendar information and an individualized-connection calendar information, utilizing a list parameter to indicate relative size relationships among a plurality of current the intermediately stored transmission rates, and determining the currently allowed transmission rate and updating the list parameter using the list parameter.
The basic aspect of the inventive method is in intermediately storing: 1) a per-call specific transmission rate of ATM cells (if it exists), and 2) appertaining time change information (if it exists); these are stored in a memory unit in the determination of the currently allowed transmission rate of ATM cells of virtual connections with variable transmission rates. They are, in addition, stored with the assistance of time change information within an ATM communication system allocated to transmission rate changes. Furthermore, the calculation of the time change information of transmission rate changes ensues with the assistance of two per-call prescribable delay times, ensuing with a transmission rate handling routine. The time change information following the expiration of a predetermined time span are updated by an updating routine with the assistance of a current time value, a calendar information and an individualized-connection calendar information.
The plurality of current intermediately stored transmission rates and their size relationship relative to one another is displayed with the assistance of a list parameter, whereby the determination of the currently allowed transmission rate and an updating of the list parameter value ensues with the assistance of the list parameter value. The employment of a simple, additional list parameter yields the advantage that the maximum transmission rate of ATM cells defined in the proposal I.371.1, xe2x80x9cTraffic Control and Congestion Control in B-ISDN: Conformance Definitions for ABT and ABRxe2x80x9d of the ITU is not required in the inventive method, and, thus, need not be stored and processed. This eliminates the use of memory and dynamically relieves the ATM communications system, even in light of the dynamically processed list parameter.
Moreover, the updating of the currently allowed transmission rate of ATM cells can be decoupled in time from the transmission rate handling routine with the assistance of the list parameter so that a non-time-critical implementation of the inventive method is possible compared to the proposed method in the communication means cited in ITU I.371.1. It is thereby especially advantageous in the inventive method that no individualized-connection counters representing the time change information are requiredxe2x80x94the currently allowed transmission rate are matched to the transmission rate change after the counters run down. Inventively, this adaptation of the currently allowed transmission rate ensures when the currently allowed transmission rate is made available for the monitoring procedure. This more uniformly distributes the load on the control unit of the ATM communication system and reduces peak loads that occur.
According to a further development of the inventive method, the individualized-connection determination of the currently allowed transmission rate of ATM cells for a virtual connection is implemented either upon arrival of an ATM cell in a first transmission direction or with the arrival of a resource management cell in a second transmission direction directed opposite to the first or after an expiration of the predetermined time span in the ATM communication system.
The adaptation of the currently allowed transmission rate can be advantageously implemented at different points in time and is not fixed in time by the run-down of an individualized-connection counter representing the time change information. This achieves flexibility in the sequence of the handling of the individual method steps for determining the currently allowed transmission rate, and particularly enables an advantageous utilization of the computer resources of the ATM communication system.
When the value of the list parameter is a first list parameter value, advantageously, no current transmission rate of ATM cells is intermediately stored. When this list parameter is a second list parameter value, a first, current transmission rate of ATM cells is intermediately stored. When the list parameter is a third list parameter value, two current transmission rates are intermediately stored, whereby the first transmission rate is lower than the second transmission rate. Finally, when the list parameter is a fourth list parameter value, two current transmission rates are intermediately stored, whereby the first transmission rate is higher than the second transmission rate.
This means that, using a small information scope (2 bits), information about the plurality of existing, current transmission rates and their size relationships relative to one another are imaged onto the list parameter. The list parameter value thus represents information about the constellation of the intermediately stored transmission rates that, for example, must be respectively re-calculated in the method disclosed in the ITU I.371.1 when the previous information about the constellation of the intermediately stored transmission rates is required for the execution of the method.
According to an advantageous development of the inventive method, a first time change information is allocated to a first current intermediately stored transmission rate, and a second time change information is allocated to a second, current intermediately stored transmission rate. The allocation of the current intermediately stored transmission rates to the time change information is adapted to the ITU-I Standard I.371.1.
According to a further development of the inventive method, a current, individualized-connection time value is allocated to the current time value given a coincidence of the calendar information with the individualized-connection calendar information; otherwise, the sum of the current time value and the predetermined time span is allocated to the current, individualized-connection time value.
Subsequently, when the presence of a current individualized-connection time value is higher than the second, intermediately stored time change information, the value of the second, current intermediately stored transmission rate is subsequently allocated to the currently allowed transmission rate when the list parameter is a third or fourth list parameter value and the first list parameter value is allocated to the list parameter.
Otherwise, when the presence of a current individualized-connection time value is higher than the first intermediately stored time change information, the value of the first, current intermediately stored transmission rate is allocated to the currently allowed transmission rate, the value of the second, current intermediately stored transmission rate is allocated to the first, current intermediately stored transmission rate, the value of the second time change information is allocated to the first time change information, and the second is allocated to the list parameter.
When the list parameter is a second list parameter value, the value of the first current intermediately stored transmission rate is allocated to the currently allowed transmission rate when a current individualized-connection time value is higher than the first intermediately stored time change information and the first list parameter value is allocated to the list parameter, and no updating of the intermediately stored time change information, of the currently allowed transmission rate, and of the list parameter is implemented at a first list parameter value.
This advantageous updating of the currently allowed transmission rate with the assistance of the list parameter enablesxe2x80x94among other thingsxe2x80x94an especially simple, circuit-oriented realization within the ATM communication system.
A further advantage of the inventive method is that an explicit transmission rate is read from an incoming resource management cell communicated in the second transmission direction and is intermediately stored in the ATM communication system. This explicit transmission rate represents the currently possible transmission rate transmittable in the first transmission direction in a further ATM communication system, and the further ATM communication system enters this explicit transmission rate into the resource management cell with the currently possible transmission capacity. The reading and intermediate storing of the explicit transmission rate is adapted to the ITU-I Standard I.371.1.
Advantageously, the two individualized-connection prescribable delay times are represented by a first delay time representing a transmission rate increase, and by a second delay time representing a transmission rate decrease, whereby the first delay time is shorter than the second delay time. The representation of an increase or decrease in transmission rate by two individualized-connection prescribable delay times is adapted to the ITU-I Standard I.371.1.
Further advantageous developments of the inventive method can be derived from the discussion below.